import java.util.Scanner;

/**
 * Created with IntelliJ IDEA.
 * Description: 牛客网.简单题.求平均数
 */

class Main {

    public static void main(String[] args) {
        Scanner scan = new Scanner(System.in);

        //write your code here......
        double sum = 0;
        int count = 0;
        double num = 0;
        while((num = scan.nextInt()) > 0) {
            count++;
            sum += num;
        }
        double avg = sum / count;
        //输出格式为：System.out.println(String.format("%.2f",avg));
        System.out.println(String.format("%.2f",avg));

    }
}

public class Test {
}
